kernel: fix mtd partition erase < parent_erasesize writes

This bug applied where mtd partition end address,
or erase start address, was not cleanly divisible by parent mtd erasesize.

This error would cause the bits following the end of the partition
to the next erasesize block boundary to be erased,
and this partition-overflow data to be written to the partition erase
address (missing additional partition offset address)
of the mtd (top) parent device.

Fixes: FS#2428

Signed-off-by: John Thomson <[email protected]>
Tested-by: Tomasz Maciej Nowak <[email protected]>
[shorten commit title, add Fixes, fix kernel 4.19 as well]
Signed-off-by: Adrian Schmutzler <[email protected]>

target/linux/generic/pending-4.19/411-mtd-partial_eraseblock_write.patch

@@ -19,7 +19,7 @@ Signed-off-by: Felix Fietkau <[email protected]>
  /* Our partition linked list */
  static LIST_HEAD(mtd_partitions);
  static DEFINE_MUTEX(mtd_partitions_mutex);
-@@ -220,6 +222,53 @@ static int part_erase(struct mtd_info *m
+@@ -220,11 +222,77 @@ static int part_erase(struct mtd_info *m
  {
  	struct mtd_part *part = mtd_to_part(mtd);
  	int ret;
@@ -73,10 +73,9 @@ Signed-off-by: Felix Fietkau <[email protected]>
  
  	instr->addr += part->offset;
  	ret = part->parent->_erase(part->parent, instr);
-@@ -227,6 +276,24 @@ static int part_erase(struct mtd_info *m
+ 	if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
  		instr->fail_addr -= part->offset;
- 	instr->addr -= part->offset;
- 
++
 +	if (mtd->flags & MTD_ERASE_PARTIAL) {
 +		if (partial_start) {
 +			part->parent->_write(part->parent,
@@ -95,10 +94,10 @@ Signed-off-by: Felix Fietkau <[email protected]>
 +		kfree(erase_buf);
 +	}
 +
- 	return ret;
- }
+ 	instr->addr -= part->offset;
  
-@@ -539,19 +606,22 @@ static struct mtd_part *allocate_partiti
+ 	return ret;
+@@ -539,19 +607,22 @@ static struct mtd_part *allocate_partiti
  	remainder = do_div(tmp, wr_alignment);
  	if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
  		/* Doesn't start on a boundary of major erase size */

target/linux/generic/pending-4.19/412-mtd-partial_eraseblock_unlock.patch

@@ -20,7 +20,7 @@ Signed-off-by: Tim Harvey <[email protected]>
 
 --- a/drivers/mtd/mtdpart.c
 +++ b/drivers/mtd/mtdpart.c
-@@ -306,7 +306,16 @@ static int part_lock(struct mtd_info *mt
+@@ -307,7 +307,16 @@ static int part_lock(struct mtd_info *mt
  static int part_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
  {
  	struct mtd_part *part = mtd_to_part(mtd);

target/linux/generic/pending-5.4/411-mtd-partial_eraseblock_write.patch

@@ -19,7 +19,7 @@ Signed-off-by: Felix Fietkau <[email protected]>
  /* Our partition linked list */
  static LIST_HEAD(mtd_partitions);
  static DEFINE_MUTEX(mtd_partitions_mutex);
-@@ -206,6 +208,53 @@ static int part_erase(struct mtd_info *m
+@@ -206,11 +208,77 @@ static int part_erase(struct mtd_info *m
  {
  	struct mtd_part *part = mtd_to_part(mtd);
  	int ret;
@@ -73,10 +73,9 @@ Signed-off-by: Felix Fietkau <[email protected]>
  
  	instr->addr += part->offset;
  	ret = part->parent->_erase(part->parent, instr);
-@@ -213,6 +262,24 @@ static int part_erase(struct mtd_info *m
+ 	if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
  		instr->fail_addr -= part->offset;
- 	instr->addr -= part->offset;
- 
++
 +	if (mtd->flags & MTD_ERASE_PARTIAL) {
 +		if (partial_start) {
 +			part->parent->_write(part->parent,
@@ -95,10 +94,10 @@ Signed-off-by: Felix Fietkau <[email protected]>
 +		kfree(erase_buf);
 +	}
 +
- 	return ret;
- }
+ 	instr->addr -= part->offset;
  
-@@ -525,19 +592,22 @@ static struct mtd_part *allocate_partiti
+ 	return ret;
+@@ -525,19 +593,22 @@ static struct mtd_part *allocate_partiti
  	remainder = do_div(tmp, wr_alignment);
  	if ((slave->mtd.flags & MTD_WRITEABLE) && remainder) {
  		/* Doesn't start on a boundary of major erase size */

target/linux/generic/pending-5.4/412-mtd-partial_eraseblock_unlock.patch

@@ -20,7 +20,7 @@ Signed-off-by: Tim Harvey <[email protected]>
 
 --- a/drivers/mtd/mtdpart.c
 +++ b/drivers/mtd/mtdpart.c
-@@ -292,7 +292,16 @@ static int part_lock(struct mtd_info *mt
+@@ -293,7 +293,16 @@ static int part_lock(struct mtd_info *mt
  static int part_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
  {
  	struct mtd_part *part = mtd_to_part(mtd);